Flexible stretch hose having inwardly extending web portions connecting adjacent pairs of reinforcing coils, with hose properties enhanced by annealing

Abstract

A flexible, stretchable, crush resistant hose particularly well suited for supplying breathing gases to patients in medical applications and the like has a helix defined by reinforcing coils of thermoplastic material, and a web of thermoplastic material bonded or welded to adjacent ones of the coils, preferably near outer diameter portions of the coils. The web extends radially inwardly between the adjacent pairs of the reinforcing coils to define a helical reverse-direction crease that can be located closer to or farther from a centerline of the hose than is the inner diameter of the reinforcing coils. The thermoplastic material of the hose is stress relieved by an annealing process performed during axial compression of the hose at a time after the hose has been formed.

What is claimed is: 
     
       1. A method of forming a flexible, stretchable, crush resistant axially extending hose, comprising the steps of providing coils entirely of thermoplastic material to form a continuous helix of substantially constant diameter, providing a thin, narrow, elongate web of thermoplastic material that extends between adjacent coils of the helix and has edge regions welded to adjacent ones of the coils to form a single continuous wall with the web having a radially inwardly extending, centrally located fold situated between adjacent ones of the coils, and enhancing the flexibility of the hose by subjecting the hose to an annealing process while axially compressing the hose so that molecules of the thermoplastic material forming the coils of the helix and the thin elongate web are relaxed such that stress is substantially absent from the hose when the coils of the helix are close together. 
     
     
       2. The method of  claim 1  wherein the annealing process is completed while the hose is axially compressed to a minimal length normal condition wherein the coils of the helix are side-by-side snugly sandwiching radially inwardly extending portions of the web therebetween to give the resulting hose a memory of the normal condition to which the hose will tend to return when released from external force influences. 
     
     
       3. The method of  claim 1  wherein the coils of the helix are formed to have a substantially uniform generally rectangular cross-sectional configuration that defines both the maximum outer diameter of the hose, and the minimum inner diameter of the hose when the hose is in its normal minimal length condition. 
     
     
       4. The method of  claim 2  wherein the hose is formed such that, when the hose is in the normal condition, portions of the web that extend radially inwardly define a reverse-direction crease at a location spaced radially outwardly from the minimum inner diameter of the hose. 
     
     
       5. The method of  claim 4  additionally including the step of utilizing the annealing process to set the reverse-direction crease. 
     
     
       6. The method of  claim 1  additionally including the steps of forming the coils of the helix with a substantially uniform cross-section, and forming the material of the web to have a substantially uniform thickness. 
     
     
       7. The method of  claim 1  wherein the step of providing thermoplastic material to form the helix and the step of providing thermoplastic material to form the web include providing the same thermoplastic material. 
     
     
       8. The method of  claim 1  wherein the step of providing the thermoplastic material to form the helix includes providing thermoplastic material selected from among polyvinyl chloride (PVC), thermoplastic urethane (TPU), polypropylene (PP), thermoplastic elastomer (TPE) and acrylonitrile butadiene styrene (ABS), and the step of providing thermoplastic material to form the web includes providing thermoplastic material selected from among PVC, TPU, PP, TPE and ABS thermoplastic. 
     
     
       9. The method of  claim 2  wherein the hose is provided with spring tension tending to cause the hose to retract to the normal condition that builds up in the hose only when the hose is stretched, with the spring tension being attributable to the thermoplastic material forming the web in proportion to the spring tension attributable to the thermoplastic material forming the coils of the support spiral being 25% to 50%. 
     
     
       10. The method of  claim 1  wherein different thermoplastic materials are used to form the helix and the web, with the thermoplastic material forming the helix being selected to have a higher modulus of elasticity than that of the thermoplastic material forming the web. 
     
     
       11. The method of  claim 2  wherein the thermoplastic materials selected to form the hose provide a stretch ratio of the length to which the hose can be stretched in comparison to the length of the hose in the normal condition that is at least 1.5:1. 
     
     
       12. The method of  claim 1  wherein the thermoplastic materials selected to form the hose provide a spring constant effective when the hose is stretched that has a value of 5 N/m to 25 N/m, with these values being determined by the thickness of the web and the nature of the material selected to form the web. 
     
     
       13. A method of forming a flexible, stretchable, crush resistant axially extending hose, comprising helically winding newly extruded thermoplastic material to form the hose to have coils that form a continuous helix of substantially constant diameter, and a thin, narrow, elongate web that extends between adjacent coils of the helix and has edge regions welded to adjacent ones of the coils to form a single continuous wall, wherein the web has a radially inwardly extending, centrally located fold situated between adjacent ones of the coils; and annealing the hose to enhance the flexibility of the hose while the coils of the helix are compressed to cause the molecules of the thermoplastic material forming the coils and the thin thermoplastic material forming elongate web to be relaxed such that stress is substantially absent from the hose when the coils of the helix are closer together. 
     
     
       14. The method of  claim 13  wherein the annealing process is completed while the hose is axially compressed to a minimal length condition wherein the coils of the helix are side-by-side snugly sandwiching radially inwardly extending portions of the web therebetween. 
     
     
       15. The method of  claim 2  wherein the hose is provided with spring tension tending to cause the hose to retract to the normal condition that builds up in the hose only when the hose is stretched, with the spring tension being attributable to the thermoplastic material forming the web in proportion to the spring tension attributable to the thermoplastic material forming the coils of the support spiral being 25% to 90%.